Okay.
Let's look at the first question.
What's the optimum pH for each enzyme?
Take a look at the graph.
Do you see how there are two lines that form hills, on that graph?
Each hill is an enzyme.
The solid hill is enzyme A,
and the dotted hill is enzyme B.
Now, look at the top of each hill.
The top of each hill is the point where the enzymes work at their best.
Question #1 calls it the "optimum," you see there.
Look at the top of each hill.
What are the pH numbers, for each of the highest points, on each hill?
(You can see the pH number line, across the bottom of the graph.)

Yes! Close enough.
Enzyme A looks to be about 3.
Enzyme B actually looks like it's a liiiiittle higher than 7. Let's say 7.5, kay?
So, let's look at the question again:
What is the optimum pH for Enzyme A and Enzyme B?
We have our answer now.
The optimum pH for Enzyme A is 3
and the optimum pH for Enzyme B is 7.5.
The "optimum pH" is the pH level where the enzymes work their best.

Okay, we're onto question #2.
Take a look at the graph, with me.
Across the bottom of the graph, we have the pH number line. Yes?
And on the left side of the graph, we have the "rate of enzyme action," you see?
Now, take a look at the graph, and find the place where the pH is 5.
What do you notice about the rates, of each enzyme, when the pH is 5?

Now, we're on to question #3.
The instructions told us that Enzyme A is in the stomach,
and Enzyme B is in the intestines.
Question #3 is asking us...
What can you tell, about the pH of the stomach?
Let's look at enzyme A, which is found in the stomach.
We know that Enzyme A works its best, when the pH is 3. Right?
So, would you agree that the pH level in the stomach is around 3?

Now, we're on to question #4.
It's asking us what we can tell about the pH of the intestine.
So NOW we have to look at Enzyme B.
And we do the same thing we did with question #3,
only this time, we're looking at Enzyme B.
Do you think you have an answer?

Okay, now we're on to question #5.
It sounds more complicated than it is.
Let me go over some facts that we already know:
1. Enzyme B is found in the intestine.
2. Enzyme B can ONLY work, when the pH is anywhere from 4 to 12.
(You can take another look at the graph, and see that the dotted line only goes from 4 to 12.)
3. Enzyme B works its best, when the pH is 7.5.
Do you understand all of these facts, so far?

It's okay, I understand.
Let's get back into question #5.
The question is asking us to pretend that Enzyme A is in the intestines.
Let me ask you two questions here:
1. What is the pH range where Enzyme A can work? (From what number, to what number?)
2. What is the "relative pH" of the intestine, that we've mentioned before?

So we know that Enzyme A would not work, in the intestine.
Because its working pH is 0 to 6.
But the intestine's pH is 7.5. Too high.
Now here's another fact:
The digestive system needs working enzymes, in order to function.
If the digestive system did not have working enzymes,
then the digestive processes would stop.
Does that make sense to you?